Republican front-runner Donald Trump is worried about rival Marco Rubio.

Discussing the proposed changes to the party’s presidential debates in a Monday interview with Bloomberg Politics’ “With All Due Respect,” Trump found a way to get in a dig at the Florida senator, saying he hoped the debate venues would be better air conditioned in the future.

“[Rubio] is the one that sweats the most,” Trump said at New York’s Wollman ice skating rink. “He’s the youngest but I have never seen any human being sweat like that.”

“He’s the youngest but I have never seen any human being sweat like that.”
Donald Trump

Trump repeatedly jabbed at Rubio, calling him “highly overrated.”